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RatFink
Joined: 01 May 2004
Posts: 49
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| Need simple code help please. |
 Posted: Sun May 02, 2004 1:01 am |
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I'm using a PIC16F77.A to control a small electronics project of mine, this is my first time trying this and it seems my one semester of C Language isn't helping much.
I just need a set of push button switches to give me an output to control some relays, but I just just can't seem to get it right. I'm pretty sure I have the push buttons and relays set up correctly (electronics I understand) but I just can't seem to get the code right. Could someone look at this for me and tell me what I'm doing wrong?
| Code: | #include <16f877A.h>
#device ICD=TRUE
#fuses HS,NOWDT,NOPROTECT
//#byte TRISA = 0x85
//#byte PORTA = 0x05
#byte TRISB = 0x86
#byte PORTB = 0x06
#byte TRISD = 0x88
#byte PORTD = 0x08
#byte ADCON0 = 0x1F
#byte ADCON1 = 0x9F
#byte ADRESH = 0x1E
#byte OPTION = 0x81
#bit T0IF = 0x0B.2
#bit GO = 0x1F.2
#bit ADIF = 0x0c.6
/* Define Outputs */
#bit Paint = PORTD.0
#bit Preheat = PORTD.1
#bit Plastic = PORTD.2
#bit Metal = PORTD.3
/* Define Inputs */
#bit PB_Paint = PORTB.0
#bit PB_Preheat = PORTB.1
#bit PB_Plastic = PORTB.2
#bit PB_Metal = PORTB.3
#use delay(clock=20000000)
#use rs232(DEBUGGER)
void main(void)
{
ADCON0 = 0x41; /* Fosc/8, A/D enabled */
OPTION = 0x07; /* TMR0 prescaller, 1:256, PORTB pullups */
ADCON1 = 0x0E; /* Left justify, 1 analog channel, VDD and Vss references */
//TRISA = 0; /* PORTA all outputs */
TRISB = 0xFF; /* PORTD all inputs */
TRISD = 0; /* PORTB all 0utputs */
Paint = 0; /* Clear Paint */
Preheat = 0; /* Clear Preheat */
Plastic = 0; /* Clear Plastic */
Metal = 0; /* Clear Metal */
BACK: do
{;}
while (PB_Paint&PB_Preheat&PB_Plastic&PB_Metal == 1);
if (PB_Paint = 0)
{
Paint = 1;
printf("Paint");
}
else if (PB_Preheat = 0)
{
Preheat = 1;
printf("Preheat");
}
else if (PB_Plastic = 0)
{
Plastic = 1;
printf("Plastic");
}
else if (PB_Metal = 0)
{
Metal = 1;
printf("Metal");
}
goto BACK; /* Check again */
} |
And here's part of the assembly code, it seems that my if/else statements don't do anything.
| Code: | ....................
.................... BACK: do
.................... {;}
.................... while (PB_Paint&PB_Preheat&PB_Plastic&PB_Metal == 1);
....................
.................... if (PB_Paint = 0)
0020: MOVLW 00
0021: BTFSC 06.0
0022: MOVLW 01
0023: MOVWF 21
0024: MOVLW 00
0025: BTFSC 06.1
0026: MOVLW 01
0027: ANDWF 21,W
0028: MOVWF 22
0029: MOVLW 00
002A: BTFSC 06.2
002B: MOVLW 01
002C: ANDWF 22,W
002D: MOVWF 23
002E: MOVLW 00
002F: BTFSC 06.3
0030: MOVLW 01
0031: SUBLW 01
0032: BTFSC 03.2
0033: GOTO 036
0034: MOVLW 00
0035: GOTO 037
0036: MOVLW 01
0037: ANDWF 23,W
0038: XORLW 00
0039: BTFSS 03.2
003A: GOTO 020
.................... {
.................... Paint = 1;
.................... printf("Paint");
....................
.................... }
....................
....................
.................... else if (PB_Preheat = 0)
.................... {
.................... Preheat = 1;
.................... printf("Preheat");
....................
.................... }
....................
....................
.................... else if (PB_Plastic = 0)
.................... {
.................... Plastic = 1;
.................... printf("Plastic");
....................
.................... }
....................
....................
.................... else if (PB_Metal = 0)
.................... {
.................... Metal = 1;
.................... printf("Metal");
....................
.................... }
....................
....................
....................
.................... goto BACK; /* Check again */ |
Thank you for any help you can give, I've spent all day trying to figure this out, and I've searched every where for answers. |
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hillcraft
Joined: 22 Sep 2003
Posts: 101
Location: Cape Town (South africa)
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| Need simple code help please. |
| Posted: Sun May 02, 2004 1:32 am |
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This is an age old common mistake.
>>else if (PB_Preheat = 0)
All that you are doing is setting the PB_Preheat variable equal to zero.
You must use == to test for equality in C
So all the else if must be changed to == |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Posted: Sun May 02, 2004 11:16 am |
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This will always evaluate to TRUE because you are using the assignment operator "=" instead of the equality operator "==". You seem to have done this in several places.
Also, unless you are intending to use more than one brand of compiler you don't need to go to all the trouble of setting up registers yourself. The CCS compiler has a rich set of built-in functions for dealing with perpherals.
And finally, typically, you don't see the "goto" statement used much as it is considered bad practice. Use a do-while-, while- or for-loop instead.
| Code: |
do {
// all my code to repeat over and over and over
} while(1);
|
--- or ---
| Code: |
while (1) {
// all my code to repeat over and over and over
} |
The key difference is that a do-while is a "bottom tested loop" and so is guaranteed to run at least once and the while{} loop is a "top tested loop" and depending on what you put in as the expression, may not run at all.
A third choice is the for{} loop
This you can make behave like the while{} loop by fiddling with the expression at the top or like the do-while loop by including an if-test at the bottom with a "break" statement.
Right off the top of my head I don't remember which form the CCS compiler is the best at implementing. But since you have figured out that the LST file is your friend you can play around and decide for yourself! :-)
A classroom is fine but the C language (and any programming language for that matter) has enough little gotcha's that the best way to learn is to practice!
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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RatFink
Joined: 01 May 2004
Posts: 49
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| Posted: Sun May 02, 2004 1:31 pm |
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Thank you guys, I can't believe I misses the "=" instead of "==", I was tearing my hair out wondering why it wouldn't work.
| Quote: | | Also, unless you are intending to use more than one brand of compiler you don't need to go to all the trouble of setting up registers yourself. The CCS compiler has a rich set of built-in functions for dealing with perpherals. |
But that would require research, which is work  I'll look into it, simple would be best.
Also, I'm not sure what you mean by the goto statement, I thought I was using a "do/while" statement, I'll check and see what you mean.
All I've had in school for C programming was just a quick overview, not really to teach me how to write it, mostly just so that if I ran into it I would know what I was looking at. |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Posted: Sun May 02, 2004 1:45 pm |
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Invest in a copy of C Programming Language (2nd Edition) by Kernighan and Ritchie, ISBN 0131103628. Should be less than $40 new and you can probably find a used copy for less. If you get a used one, just make sure it is the 2nd edition and not the first.
Lots of other good C books out there but this one still holds up well after 26 years (16 for the 2nd edition)!
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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